Presently, a wide variety of foods are canned and pasteurized to prevent microbial spoilage by heating the canned product under high pressure, i.e., in a retort, for a period of time and at a temperature sufficient to render the product commercially sterile. However, the time and temperature needed for commercial sterility generally results in overcooking of the food.
As an example, in retort processing of an Italian pasta, meat balls and sauce product, meat is formed into meat balls by extrusion, browned and added in appropriate numbers to cans. Pasta is extruded, blanched and similarly added to the cans. After adding sauce, the cans are sealed and heated in a retort to effect cooking of the ingredients as well as pasteurization. The pasta is generally overcooked, soft and undesirable.
An alternate system of pasteurization has been developed which relies upon the inability of certain harmful organisms to be viable under reduced pH. The processing of foods under acidic conditions of an equilibrium pH of 4.6 and below requires a lesser period of heating at a lower temperature than that used for retort canning to thereby avoid the loss of organoleptic properties due to excessive cooking. While this method avoids excessive cooking, it also requires that each ingredient be cooked prior to pasteurization.
It is desirable to cook the meat balls in the sauce to avoid loss of flavoring components from the meat. However, the small meat balls as used in this type of product tend to float in sauce so that accurate filling of a sauce containing meat balls is not practical. Uniform filling is required so that the product in the container will be properly reflected by the ingredients statement on the label. Pasta has much different cooking requirements than, and cannot be cooked with, meat balls and/or sauce.
The use of glass as a container can be beneficial in providing a surface inert to the acid food, allow the customer to view the product and be capable of warming in a microwave oven in the original container. Many difficulties have arisen in attempting to process a pasta meat ball and sauce product as an acidified food in a glass container.
The commercial packaging of food in glass containers on mass production lines is limited by the propensity of the glass in commercial containers to shatter when subjected to thermal shock, i.e., too great a variance in temperature over too short a period of time. As an example, the manufacturer of one type of glass container specifies a standard of 21.degree. C. (70.degree. F.) as a thermal deviation standard to avoid shattering.
Glass containers in hot packing must be tempered, i.e. temperature adjusted slowly enough to avoid thermal shock, to avoid shattering upon packing. In a mass production line, a shattered container in addition to causing spilled material could present the danger of shards of glass falling into the openings of the numerous uncovered containers lined up for filling.
In the packing of liquid foods in glass containers, metering valves are used to fill the container with the proper amount of material in as fast a time as possible. If the food products are generally uniform in character, little difficulty ensues in rapid filling from the food metering valves in use today. These valves are designed such that, when opened, metering orifices or passageways are exposed. Foods with small, flexible particles such as pasta or small pieces of meat can be uniformly packed without serious abrasion of the food by blockage of the metering valve.
In contrast, large food particles can cause blockage of the metering valve and be subject to abrasion when passing through the orifices. Abrasion as well as blockage can lead to non-uniform filling of the container. For instance, in a tomato sauce containing meat balls, it is necessary to pack the meat balls separately in order to provide a product conforming to the ingredient declaration on the label, and to avoid organoleptic degradation of the meat balls. Also, meat balls tend to float in the sause making gravity filling a diffcult operation.
Further, food can be degraded by overcooking such as can occur in a commercial canning system as the food can be heated, during preparation, while awaiting packing as well as during pasteurization. In a product such as pasta and meat balls packed in sauce, each ingredient has its optimum cooking time and temperature. Cooking to the extent needed for one can overcook another. However, it is desirable to cook the meat balls in the container to avoid a loss of the flavor the meat can provide to the sauce.
The use of low acidity and short time heating achieves a level of commercial sterilization as effective as that obtained by retort pasteurization. Acid or acidified foods, as they are termed in the FDA regulations, provide better mouth feel and customer appeal than retorted foods by avoiding the overcooking that can accompany retort pasteurization. In order to qualify as an acid food, the food must have an equilibrium pH of 4.6 or below. This requires that the interior of solids such as meat balls and macaroni be acidified. To achieve levels of low interior acidity, the food can be blanched in food grade acid and packed in acidic liquid medium (U.S. Pat. No. 3,886,296). Meat emulsions can be acidified by the addition of encapsulated food grade acids such as citric acid encapsulated by fat in combination with an organic acid type preservative (U.S. Pat. No. 3,692,534) or an encapsulated acidogen (U.S. Pat. No. 4,262,027). Upon cooking, the encapsulation melts, releasing the acid or acidogen which hydrolyzes to an acid. The packing process must allow for the cooking of the solid products at the time of packing.
It has been found that these problems can be overcome by the present invention.